U.S. Secretary of State John Kerry speaks on his phone while his plane refuels at Ramstein Air Base in Ramstein-Miesenbach, Germany, on Aug. 1, 2014.

Israel reportedly eavesdropped on U.S. Secretary of State John Kerry's phone calls during last year's failed Middle East peace talks between Israel, Palestinian authorities and Arab states.

The intelligence services of Israel, as well as those of at least one other country, intercepted phone calls made by Kerry using an insecure telephone, according to a report published on Sunday by the German news magazine Der Spiegel.

Kerry would have made some of those calls to high-ranking negotiating partners using an unencrypted telephone over a satellite line, according to Der Spiegel, which cited "several intelligence service sources." Israel reportedly used the information learned while listening in on Kerry's calls in its own negotiations.

The report didn't include details on the alleged high-level surveillance, leaving many speculating as to how, and why, this could have happened.

Steven Bellovin, a professor of computer science at Columbia University, said on Twitter that Kerry could have deliberately used the unencrypted phone "to leak information he wanted [Israel] to know."

Regardless, if the report is true, it might sour the relationship between the United States and Israel a little bit more. Last week, Israeli government officials criticized Kerry for his peacemaking efforts in the current Israel and Gaza conflict.

And this wouldn't be the first time in the last few months that Israel finds itself accused of spying on its long-time ally. In May, Newsweek reported that Israel's spying efforts "crossed red lines." Israeli officials, however, responded by saying that the report was false and malicious.

When asked about this latest report, a White House spokesperson referred Mashable to the State Department, which did not respond to our request for comment. The Israeli government has also yet to respond to Der Spiegel's report.